The present invention relates to a semiconductor device and a method for fabricating the same. More particularly, the present invention relates to a semiconductor device that reduces a passing gate effect and a method for fabricating the same.
As semiconductors become highly integrated, electric characteristics such as a threshold voltage and a refresh rate requires an increase when a channel dimension decreases. Thus, a recess gate structure is introduced to increase the channel length by selectively etching a substrate.
FIG. 1A illustrates a top view of a typical semiconductor device.
FIG. 1B illustrates a cross-sectional view of the semiconductor device shown in FIG. 1A cut along a line X-X′.
Referring to FIGS. 1A and 1B, a substrate 11 where isolation region and active region 13 are defined by an insulation layer 12 is selectively etched to form a recess pattern 14. A gate insulation layer 15 is formed over the recess pattern 14. Polysilicon layer 16, tungsten layer 17, and gate hard mask layer 18 are formed over a resultant structure including the recess pattern 14. Then, a patterning process is performed thereon to form gate lines GL. Thus, a plurality of gate lines GL are formed simultaneously crossing the isolation region and the active region 13. The gate lines GL crossing the active region 13 is called a main gate and the gate lines GL crossing the isolation region is called a passing gate.
However, as semiconductor devices become highly integrated, a physical gap between the main gate and the passing gate decreases. Thus, a threshold of the main gate changes and a parasitic capacitance between the main gate and the passing gate increases due to a bias applied to the passing gate. That is, the passing gate effect occurs.
Furthermore, a portion of the isolation layer 12 is etched during an etch process for forming the recess pattern 14 in the aforementioned typical method. Generally, the isolation layer 12 is etched down to approximately ⅔ to approximately ½ of the recess pattern 14. The damage of the isolation layer 12 decreases the physical gap between the main gate and the passing gate (refer to ‘A’ area of FIG. 1B). Thus, the described passing effect becomes more intense.